After decades of searching, scientists have found no trace of extraterrestrial intelligence. Now, some of them hope to make contact by broadcasting messages to the stars. Are we prepared for an answer?

Alexander Zaitsev, Chief Scientist at the Russian Academy of Sciences’ Institute of Radio Engineering and Electronics, has access to one of the most powerful radio transmitters on Earth. Though he officially uses it to conduct the Institute’s planetary radar studies, Zaitsev is also trying to contact other civilizations in nearby star systems. He believes extraterrestrial intelligence exists, and that we as a species have a moral obligation to announce our presence to our sentient neighbors in the Milky Way—to let them know they are not alone. If everyone in the galaxy only listens, he reasons, the search for extraterrestrial intelligence (SETI) is doomed to failure.

Zaitsev has already sent several powerful messages to nearby, sun-like stars—a practice called “Active SETI.” But some scientists feel that he’s not only acting out of turn, but also independently speaking for everyone on the entire planet. Moreover, they believe there are possible dangers we may unleash by announcing ourselves to the unknown darkness, and if anyone plans to transmit messages from Earth, they want the rest of the world to be involved. For years the debate over Active SETI versus passive “listening” has mostly been confined to SETI insiders. But late last year the controversy boiled over into public view after the journal Nature published an editorial scolding the SETI community for failing to conduct an open discussion on the remote, but real, risks of unregulated signals to the stars. And in September, two major figures resigned from an elite SETI study group in protest. All this despite the fact that SETI’s ongoing quest has so far been largely fruitless. For Active SETI’s critics, the potential for alerting dangerous or malevolent entities to our presence is enough to justify their concern.

“We’re talking about initiating communication with other civilizations, but we know nothing of their goals, capabilities, or intent,” reasons John Billingham, a senior scientist at the private SETI Institute in Mountain View, California. Billingham studied medicine at Oxford and headed NASA’s first extraterrestrial search effort in 1976. He believes we should apply the Hippocratic Oath’s primary tenet to our galactic behavior: “First, do no harm.” For years Billingham served as the chairman of the Permanent Study Group (PSG) of the SETI subcommittee of the International Academy of Astronautics, a widely accepted forum for devising international SETI agreements. But despite his deep involvement with the group, Billingham resigned in September, feeling the PSG is unwisely refusing to take a stand urging broad, interdisciplinary consultation on Active SETI. “At the very least we ought to talk about it first, and not just SETI people. We have a responsibility to the future well-being and survival of humankind.”

Billingham is not alone in his dissent. Michael Michaud, a former top diplomat within the US State Department and a specialist in technology policy, also resigned from the PSG in September. Though highly aware of the potential for misunderstanding or ridicule, Michaud feels too much is at stake for the public to remain uninvolved in the debate. “Active SETI is not science; it’s diplomacy. My personal goal is not to stop all transmissions, but to get the discussion out of a small group of elites.”

Michaud is the original author of what became the “First SETI Protocol,” a list of actions to take in the event of a SETI success. In the late 1980s, several international organizations committed to its principles: First, notify the global SETI community and cooperate to verify the alien signal. Then, if the discovery is confirmed, announce it to the public. Finally, send no reply until the nations of the world have weighed in. A future “Second SETI Protocol” was meant to refine the policy for sending mes- sages from Earth, but the effort quickly became complicated. Everyone agreed that if a message were received, broad global dialogue concerning if and how to respond must take place before any reply could be sent. The rift arose over whether or not the Protocol should also address Active SETI transmissions made before any signal is detected.

At a meeting last year in Valencia, Spain, a divided PSG voted to change Michaud’s draft of the Second Protocol. They deleted language calling for “appropriate international consultations” before any deliberate transmissions from Earth, overriding the concerns of Billingham and Michaud and triggering Nature‘s editorial. As Michaud describes it, “Last fall, this became an unbridgeable gap. They brought it to a vote but there was no consensus. Those with dissenting views were largely cut out of the discussion.” Michaud and Billingham feel that by not explicitly advocating a policy of international consultations, the SETI PSG is tacitly endorsing rogue broadcasters.

Seth Shostak, the current chair of the SETI PSG, maintains that Nature got it wrong, that in Valencia there was no organized effort to discourage open and transparent debate about the wisdom of sending signals. As the SETI Institute’s senior astronomer, Shostak has been involved in the science and policy of SETI for many years, and often seems to act as public spokesman for the Institute and for SETI in general. He says it’s inappropriate for the PSG to set global guidelines for Active SETI. “Who are we to tell the rest of the world how to behave? It would be totally unenforceable.”

Michaud and Billingham agree that the PSG can’t make policy for the whole world. But rather than sweep the question under the rug, they believe it is the responsibility of the SETI community to facilitate the wider conversation that must take place. “We feel strongly that the discussion must involve not just astronomers, but a broad spectrum of social scientists, historians, and diplomats,” explains Billingham.
“This was simply about jurisdiction,” Shostak insists. The First Protocol, he says, is about self-policing; the Second isn’t. “If we found a signal, it would be a result of our own research. Therefore we felt it was responsible to have an agreed-upon policy about what to do next.” Shostak also worries that drafting guidelines for sending messages to aliens could generate bad press. SETI has always struggled for respectability. In the 1970s and 80s, NASA supported some listening programs, but government funding was cut off in 1993 amid congressional ridicule. Thanks to private funding, SETI has rebounded since then, but is still vulnerable to association with tabloids and talk radio guests claiming personal contact with aliens. Publicizing the real debate over rules of conduct for talking to extraterrestrials, Shostak reasons, wouldn’t do much to help counter this vision.

Long before he was an eager practitioner of Active SETI, Alexander Zaitsev was already a respected astronomer investigating planets using huge blasts of radar energy from the 70-meter radio telescope at the Evpatoria Deep Space Center in Crimea, Ukraine. Planetary radar studies rely on powerful, focused beams to “illuminate” distant objects, though much of this energy misses its target. The beams would be fleeting if seen from other stars that, by chance, lay along their path. But aimed and modulated to contain pictures, sounds, and other multimedia, they very easily become calling cards from Earth. On balance, it’s relatively simple to send signals, so why have we just been listening?

SETI doctrine states that anyone we hear from will almost certainly be much more advanced than we are. Simply put, our capabilities are so rudimentary that any chance of detecting an alien transmission would require that it be broadcast powerfully and continually on millennial timescales. We can’t predict much about alien civilizations, but we can use statistical mathematics to derive simple, robust relationships between the number of putative civilizations, their average longevity, and their population density in the galaxy. The chance of getting a signal from another baby race like ours is infinitesimally small. As Shostak says, “We’ve had radio for 100 years. They’ve had it for at least 1,000 years. Let them do the heavy lifting.”

This is one reason why most SETI pioneers advocated a “first, just listen” approach. But there is another: What if there is something dangerous out there that could be alerted by our broadcasts? This ground has been explored in numerous scientific papers and, of course, in countless works of science fiction. Few people alive today embody the convergence of hard science and fictional speculation better than David Brin, an author of both peer-reviewed astronomy papers and award-winning science fiction novels. In an influential 1983 paper titled “The Great Silence,” Brin provided a kind of taxonomy of explanations for the lack of an obvious alien presence. In addition to the usual answers positing that humanity is alone, or so dull that aliens have no interest in us, Brin included a more disturbing possibility: Nobody is on the air because something seeks and destroys everyone who broadcasts. Like Billingham and Michaud, he feels the PSG is dominated by a small number of people who don’t want to acknowledge Active SETI’s potential dangers.

Even if something menacing and terrible lurks out there among the stars, Zaitsev and others argue that regulating our transmissions could be pointless because, technically, we’ve already blown our cover. A sphere of omnidirectional broadband signals has been spreading out from Earth at the speed of light since the advent of radio over a century ago. So isn’t it too late? That depends on the sensitivity of alien radio detectors, if they exist at all. Our television signals are diffuse and not targeted at any star system. It would take a truly huge antenna—larger than anything we’ve built or plan to build—to notice them.

Alien telescopes could perhaps detect Earth’s strange oxygen atmosphere, created by life, and a rising CO2 level, suggesting a young industrial civilization. But what would draw their attention to our solar system among the multitudes? Deliberate blasts of narrow-band radiation aimed at nearby stars would—for a certain kind of watcher—cause our planet to suddenly light up, creating an obvious beacon announcing for better or worse, “Here we are!”

In fact, we have already sent some targeted radio messages. Even now they are racing toward their selected destinations, and they are unstoppable. Frank Drake sent the first Active SETI broadcast from the large radio telescope in Arecibo, Puerto Rico, in November 1974. In its narrow path, the Arecibo message was the most powerful signal ever sent from Earth. But it was aimed at M13, a globular star cluster about 25,000 light years away. At the earliest, we could expect a reply in 50,000 years.

Teen-Age Message

Click here to listen to Gershwin’s “Summertime,” as recorded for the Theremin concert.

More recently, Zaitsev and his colleagues sent a series of messages from their dish at Evpatoria. In 1999 and 2003 they sent “Cosmic Call” I and II, transmissions containing pictograms meant to communicate our understanding of the universe and life on Earth. In 2001, Zaitsev and a group of Russian teenagers created the “Teen-Age Message to the Stars,” which was broadcast in August and September of that year in the direction of six stars between 45 and 70 light years from Earth. The Teen-Age Message notably included greetings in Russian and English, and a 15-minute Theremin symphony for aliens. Unlike Drake’s Arecibo message, Zaitsev’s messages target nearby stars. So if anyone wishes to reply, we may receive it in the next century or two.

Both Cosmic Call transmissions included an “Interstellar Rosetta Stone” (IRS) designed by Canadian scientists Yvan Dutil and Stephane Dumas. Using simple symbols and equations, the IRS progressively builds a mathematical foundation for the introduction of our understanding of physics, chemistry, and biology, ultimately giving a glimpse of life on Earth. Here are several annotated selections from the IRS. Click to enlarge.

Along with the famous plaques attached to Pioneer 10 and 11 and the two phonograph records carried by Voyager 1 and 2—four spacecraft that will soon leave our Solar System—these messages are mostly symbolic efforts unlikely to betray our presence to the denizens of planets orbiting other stars. Our civilization is still hidden from all but those ardently searching for our kind, or those so far beyond our level of sophistication that we couldn’t hide from them if we wanted to. To date, all our “messages to aliens” are really more successful as communications to Earth, mirrors reflecting our dreams of reaching far beyond our terrestrial nursery.

For now, the dissenters have given up on the SETI PSG, but there’s still hope for a solution to the standoff. At the PSG’s 2007 meeting held in Hyderabad, India this September, the group implicitly accepted the reality of Active SETI risks by adopting a standard called the “San Marino Scale,” a formula for assessing the risk of a given broadcast program. Michaud admits that the scale “is a useful starting point for discussion.”

When pressed, everyone involved in the recent controversy agrees that harmful contact scenarios cannot be completely ruled out. Active SETI critics like Billingham, Michaud, and Brin don’t support a blanket ban on transmissions, and even Zaitsev accepts that open and multinational discussion is needed before anyone pursues transmission programs more ambitious and powerful than his own. The major disagreement is actually over how soon we can expect powerful transmission tools to become widely available to those who would signal at whim.

At present, the radio astronomy facilities potentially capable of producing a major Active SETI broadcast are all controlled by national governments, or at least large organizations responsible to boards and donors and sensitive to public opinion. However, seemingly inevitable trends are placing increasingly powerful technologies in the hands of small groups or eager individuals with their own agendas and no oversight. Today, on the entire planet, there are only a few mavericks like Zaitsev who are able and willing to unilaterally represent humanity and effectively reveal our presence. In the future, there could be one in every neighborhood.

So far SETI has turned up no evidence of other intelligent creatures out there seeking conversation. All we know for certain is that our galaxy is not full of civilizations occupying nearly every sun-like star and sending strong radio signals directly to Earth. In the absence of data, the questions of extraterrestrial intelligence, morality, and behavior are more philosophy than science. But even if no one else is out there and we are ultimately alone, the idea of communicating with truly alien cultures forces us to consider ourselves from an entirely new, and perhaps timely, perspective. Even if we never make contact, any attempt to act and speak as one planet is not a misguided endeavor: Our impulsive industrial transformation of our home planet is starting to catch up to us, and the nations of the world are struggling with existential threats like anthropogenic climate change and weapons of mass destruction. Whether or not we develop a mechanism for anticipating, discussing, and acting on long-term planetary dangers such as these before they become catastrophes remains to be seen. But the unified global outlook required to face them would certainly be a welcome development.